/*
 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */
package jdk.vm.ci.meta;

import java.util.ArrayList;
import java.util.List;

/**
 * Describes the {@link Local}s for a Java method.
 *
 * @see "https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.13"
 */
public class LocalVariableTable {

    private final Local[] locals;

    /**
     * Creates an object describing the {@link Local}s for a Java method.
     *
     * @param locals array of objects describing local variables. This array is now owned by this
     *            object and must not be mutated by the caller.
     */
    @SuppressFBWarnings(value = "EI_EXPOSE_REP2", justification = "caller transfers ownership of `locals`")
    public LocalVariableTable(Local[] locals) {
        this.locals = locals;
    }

    /**
     * Gets a description of a local variable that occupies the bytecode frame slot indexed by
     * {@code slot} and is live at the bytecode index {@code bci}.
     *
     * @return a description of the requested local variable or null if no such variable matches
     *         {@code slot} and {@code bci}
     */
    public Local getLocal(int slot, int bci) {
        Local result = null;
        for (Local local : locals) {
            if (local.getSlot() == slot && local.getStartBCI() <= bci && local.getEndBCI() >= bci) {
                if (result == null) {
                    result = local;
                } else {
                    throw new IllegalStateException("Locals overlap!");
                }
            }
        }
        return result;
    }

    /**
     * Gets a copy of the array of {@link Local}s that was passed to this object's constructor.
     */
    public Local[] getLocals() {
        return locals.clone();
    }

    /**
     * Gets a description of all the local variables live at the bytecode index {@code bci}.
     */
    public Local[] getLocalsAt(int bci) {
        List<Local> result = new ArrayList<>();
        for (Local l : locals) {
            if (l.getStartBCI() <= bci && bci <= l.getEndBCI()) {
                result.add(l);
            }
        }
        return result.toArray(new Local[result.size()]);
    }
}
